MEXICO CITY — The Mexican drug war that has largely been defined by violence along the border is intensifying in interior and southern areas once thought clear of the carnage, broadening a conflict that has already overwhelmed the authorities and dispirited the public, according to analysts and new government data.

Last week, two headless bodies were found in a smoldering minivan near the entrance to one of the largest and most expensive malls in Mexico City, generally considered a refuge from the grisly atrocities that have gripped other cities throughout the drug war.

Two other cities considered safe just six months ago — Guadalajara and Veracruz — have experienced their own episodes of brutality: 26 bodies were left in the heart of Guadalajara late last year, on the eve of Latin America’s most prestigious book fair, and last month the entire police force in Veracruz was dismissed after state officials determined that it was too corrupt to patrol a city where 35 bodies were dumped on a road in September.

The spreading violence, believed to largely reflect a widening turf war between two of the biggest criminal organizations in the country, has implications on both sides of the border, putting added pressure on political and law enforcement leaders who are already struggling to show that their strategies are working.

“It is a situation ever more complicated and complex,” said Ricardo Ravelo, a Mexican journalist who has written several books on criminal organizations. “Resources are and will be stretched to deal with this.”

U.S. officials in Mexico City acknowledge that the mayhem is unpredictable but contend that they have a way to help tackle it, spreading word that the $1.6 billion Merida Initiative, Washington’s signature anti-drug program, will step up training and advising for the Mexican state and local police and judicial institutions this year, rather than emphasizing the delivery of helicopters and other equipment.

In a year in which President Felipe Calderon’s party, in power since 2000, may struggle to hang on to the presidency in July elections, the expanding violence is giving political rivals much to run on.

Discerning patterns of violence in the drug war can be perilous; it is often like a tornado skipping across terrain, devastating one area while leaving another untouched.

But government statistics released last week showed a surge in deaths presumed to be related to drug or organized crime in Mexico state, which surrounds the capital and is the nation’s most populous state, in the first nine months of last year. The government data also show that violence has now afflicted 831 communities nationwide, an increase of 7 percent.

Although questions have emerged about the government’s tally, many analysts agree that the violence is widening.

“There has been a definite shift of violence away from the border and back to the interior states,” said David Shirk, director of the Trans-Border Institute at the University of San Diego, who closely tracks drug crime.

In a way, he said, the shift is a stark reversal of the trend of six years ago, when violence exploded in more southerly states and migrated north along drug-trafficking routes, accelerating a drug war that has now left more than 47,000 people dead, according to the government.